Abstract/Summary

• Wild and managed pollinators are threatened by the individual and combined effects of multiple environmental pressures, although some of the pressures may be beneficial or provide opportunities for pollinators. Evidence for this is drawn from the many individual studies of these impacts at different locations in Britain and elsewhere along with global analyses of available data. The precise impact of these pressures, either individually or in combination, differs between pollinator groups due to variability in ecological and evolutionary traits that predispose a species to be resistant or vulnerable to environmental changes.
• Since the 1950s, the distributions and diversity of some wild pollinator groups (e.g. bumble bees, solitary bees, butterflies and moths) have changed in Britain, with generally more areas showing a loss than an increase in species occurrence (the number of places a species is found) and diversity (number of species in a location). Hoverfly species losses have also occurred in specific locations, but there have been increases in diversity elsewhere. A recent analysis suggests, however, that the losses of wild pollinator and wild insect-pollinated plant diversity might be slowing.
• However, a lack of regular and standardised monitoring of wild bee and hoverflies means that it is not possible to know whether their population sizes (abundance) are changing along with their diversity and occurrence. The number of managed honey bee colonies has generally fallen in recent decades, although there appears to have been a recent increase in England since 2007, such patterns are probably due to environmental pressures but also socio-economic factors affecting the level of bee keeping.
• There remains much uncertainty (and research to be done) around the ecological and biological mechanisms connecting changes in pollinator biodiversity (abundance, composition, diversity, timing of life-cycle) with pollination processes and ultimately the quality and quantity of UK crop yields
• Economic benefits are derived from both commercial and wild pollinators. These benefits are associated with market and non-market values. Market-valued impacts relate to the contribution of pollinators to crop production, whilst non-market values include the pollination of wild plants and the pleasure people derive from seeing bumblebees. In terms of informing policy, the most important concept is the marginal value of pollination services. Marginal values, which relate to the effect changes in the abundance of a pollinator species have on crop economic value, are likely to vary across crops, between pollinator species, over time and among locations. However, no robust empirical estimates of such marginal values exist for UK crops.
• Wild pollinators also have an economic value in terms of the insurance service which they provide to farmers and growers, given the likelihood of sudden declines in commercial or managed pollinators due to outbreaks of pests and diseases.
• Non-market economic values relate to the direct and indirect contributions which wild pollinators make to people’s well-being, as measured through the willingness-to-pay of citizens to prevent losses or to achieve gains in wild pollinator populations. That such values exist is demonstrated by public support for organisations such as the Bumblebee Conservation Trust. However, no robust empirical estimates of such values can be found to date.
• Currently there is no all encompassing pollinator monitoring toolkit or single measure of status. Butterfly and moth species, for which there is are good data on abundance, cannot be used as a reliable proxy or indicator of decline in other pollinator species due to large ecological differences between them. Species richness and functional diversity (the species traits important to pollination contained in a community) of wild pollinators have a role in insuring pollination service delivery and can be derived from existing records of species occurrence. However, these data lack detail at small geographical and time scales, which makes them only a crude approximation of the distribution of potential ecosystem service providers in the British landscape. The abundance data needed to understand fully the delivery of pollination services to crops are totally lacking.
• From the UK National Ecosystem Assessment three scenarios (Go with the Flow, National Security and Local Stewardship) were adapted to construct narratives up to 2025 outlining potential futures for pollinators and pollination benchmarked against the present day situation.
• Regular and standardised monitoring of pollinator populations is needed to unequivocally establish whether wild insect pollinators are in decline or not, and what the predominant drivers are likely to be.
• Currently the direction and magnitude of changes in pollinator biodiversity, the value and functional relationship of pollinators to agriculture from farm to national scales and how this biodiversity and linked ecosystem service will change in the future remain only partly understood.